There are various known methods that are used to detect the presence of dental caries, including visual and tactile investigations using the usual dental explorer. These methods and instruments have their limits and cannot detect dental caries reliably, especially when the dental caries is proximal and when the decay is at an initial stage. X-ray investigation of teeth structure is also not reliable for detecting dental caries at the beginning of their formation in regions where a too great superimposition of enamel is present on the X-ray film. These obstructing superimpositions of teeth structures are more typical for the occlusal aspect of the teeth, and when the angle between the teeth alignment and the X-ray irradiation axis induces superimposition. The X-ray evaluation technique also exposes the patient to potentially harmful radiations.
Transillumination is another technique used to detect dental caries. By irradiating visible light toward a tooth from an aspect (e.g. lingual) and by observing via another aspect (e.g. buccal) the transmitted light, the operator can sometimes confirm the diagnosis of dental caries by observing a luminosity contrast induced by a dental caries. This technique is not suitable for all dental caries, especially for dental caries at their beginning phase. Furthermore the device used for transillumination detection of caries is large and not easy to manipulate in the mouth.
Other devices have been devised for the detection of dental caries using luminescence or fluorescence spectroscopy with variable efficiencies depending, amongst others, on the cleanliness of the tooth surface. When irradiated with one or more initial radiations at a specific wavelength, some tooth structures generate a second radiation with a wavelength that is different from the initial radiations. The intensity and wavelength of such a second radiation is different for sound tooth structures from those for decayed tooth structures. See U.S. Pat. No. RE31,815, U.S. Pat. No. 4,479,499, U.S. Pat. No. 6,186,780, U.S. Pat. No. 6,102,704, U.S. Pat. No. 6,053,731, U.S. Pat. No. 6,135,774 and U.S. Pat. No. 5,306,144, and German Patent Publications No. DE-30 31 249-C2, No. DE-42 00 741-A1, No. DE-U1-93 17 984, No. DE-303 1249-C2 and No. DE-19541686-A1. In most cases, these devices include a laser to generate the initial exciting radiation, which can be potentially harmful to the patient.
The above described optical approaches are however sometimes inadequate for the detection of interproximal caries. Different approaches have been suggested with a view to better detect interproximal caries. These approaches are mostly based on special probes that try to reach the interproximal area. The making and manipulation of such probes are complex and not convenient.
There is therefore a need for improved optical method for the detection of caries and in particular interproximal caries.